# CVE-2026-15709: libsoup WebSocket unbounded decompression memory exhaustion

Source: https://junglewise.ai/threats/cve-2026-15709-libsoup-websocket-unbounded-decompression-memory-exhaustion  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-14. Updated: 2026-07-14  
License: CC BY 4.0 with a link back

CVE-2026-15709 · Severity: high · CVSS 7.5 · Published 2026-07-14

libsoup, a widely used HTTP client/server library for GNOME and GTK applications, is vulnerable to a 'decompression bomb' attack. An attacker can send a small, specially crafted compressed message that expands to a massive size when processed, exhausting the system's memory. This results in the affected application crashing, leading to a denial of service for users of web browsers like Epiphany or other desktop applications that rely on this library for WebSocket communications.

Technologies: [Gnome Libsoup](https://junglewise.ai/threats/technologies/libsoup), [Red Hat Enterprise Linux 10](https://junglewise.ai/threats/technologies/enterprise-linux-10), [Red Hat Enterprise Linux 8](https://junglewise.ai/threats/technologies/enterprise-linux-8), [Red Hat Enterprise Linux 9](https://junglewise.ai/threats/technologies/enterprise-linux-9). Vendors: [Gnome](https://junglewise.ai/threats/vendors/gnome), [Red Hat](https://junglewise.ai/threats/vendors/red-hat).

## Quick answers

**Is CVE-2026-15709 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-15709 being exploited in the wild.

**How severe is CVE-2026-15709?** High severity, with a CVSS score of 7.5, published 14 July 2026.

**Which products and versions are affected?** Gnome Libsoup 3.2.3, 3.7.0.

**Is there a fix for CVE-2026-15709?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-15709 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-15709?** Check whether you run Gnome Libsoup, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8 or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A vulnerability exists in libsoup's WebSocket permessage-deflate extension due to improper handling of highly compressed data (CWE-409). The decompression loop in `soup-websocket-extension-deflate.c` uses `inflate()` to process data in chunks and dynamically grows a `GByteArray` buffer without enforcing an upper bound during the process. While `max_incoming_payload_size` limits the compressed size on the wire, the check for decompressed size (`max_total_message_size`) occurs only after decompression is complete. Furthermore, `max_total_message_size` defaults to unlimited for client connections. An unauthenticated remote attacker can send a small compressed frame (e.g., <128KB) that expands to hundreds of megabytes, triggering an Out-of-Memory (OOM) crash before the library can reject the message.

## Affected products

- GNOME libsoup 3.2.3, 3.7.0
- Red Hat Red Hat Enterprise Linux 8
- Red Hat Red Hat Enterprise Linux 9
- Red Hat Red Hat Enterprise Linux 10

## Timeline

- 2026-07-14: disclosed: Vulnerability reported via Red Hat and GNOME GitLab
- 2026-07-14: advisory: CVE-2026-15709 published

## References

- [https://access.redhat.com/downloads/content/package-browser/](https://access.redhat.com/downloads/content/package-browser/)
- [https://access.redhat.com/security/cve/CVE-2026-15709](https://access.redhat.com/security/cve/CVE-2026-15709)
- [https://bugzilla.redhat.com/show_bug.cgi?id=2499922](https://bugzilla.redhat.com/show_bug.cgi?id=2499922)
- [https://gitlab.gnome.org/GNOME/libsoup/-/issues/511](https://gitlab.gnome.org/GNOME/libsoup/-/issues/511)

## Related threats

- [libsoup HTTP request smuggling via undrained Expect: 100-continue body](https://junglewise.ai/threats/cve-2026-103399-a-flaw-was-found-in-soupserver-libsoup-when-an-http-1-x-client)
- [libsoup heap buffer overflow in permessage-deflate WebSocket extension](https://junglewise.ai/threats/cve-2026-102560-a-flaw-was-found-in-libsoup-when-the-permessage-deflate)
- [libsoup heap buffer overflow in WebSocket handling](https://junglewise.ai/threats/cve-2026-102558-a-flaw-was-found-in-libsoup-when-max-incoming-payload-size-is)
- [libsoup out-of-bounds read in data-URI base64 decoding](https://junglewise.ai/threats/cve-2026-102555-a-flaw-was-found-in-libsoup-the-soup-uri-decode-data-uri)
- [libsoup heap corruption in WebSocket message reassembly](https://junglewise.ai/threats/cve-2026-102557-a-flaw-was-found-in-libsoup-when-reassembling-fragmented)